1. Field of the Invention
The present invention relates to an optical sensor module which detects the motion of light irradiated from light emitting diodes (LEDs) such that a button function of a mobile electronic apparatus can be implemented in a non-contact manner.
2. Description of the Related Art
In general, a character input of small-sized mobile electronic apparatuses including mobile phones is carried out by pressing or touching a key pad.
The reason why an input method using such a key pad is mainly used in small-sized mobile electronic apparatuses is that there is a limit in the thickness of sensor modules used in other input methods. Further, when sensor modules with a relatively large thickness are used, there are difficulties in reducing the size of small-sized electronic apparatuses including mobile phones.
In one of the other input methods, a Graphic User Interface (GUI) environment such as a figure or character plate or the Window of a computer is implemented on an LCD screen. Then, a cursor is moved to input a figure or character, or to click an icon, thereby carrying out a menu input.
In this method, as a finger (object) is moved on an optical sensor module so as to move a cursor on a screen, a specific figure or icon is input. Therefore, the finger (object) is moved on the optical sensor module so as to click a specific figure, character, or icon. When the finger (object) is separated, an input or cancellation of the selected figure, character, or icon is carried out.
Such an optical sensor module is applied to an optical mouse for transmitting an input signal to a computer. In the optical sensor module applied to the optical mouse, an object surface faces downward. Therefore, light from a light source is irradiated downward. Further, a lens is positioned in a lower portion of the optical image sensor such that a cursor on the screen is moved by the motion of the optical mouse.
To apply such an optical sensor module to small-sized electronic apparatuses such as mobile phones, a finger (object) should be moved from an upper direction of the object surface such that the motion thereof is detected. Therefore, the surface of the optical sensor module should face upward, and a lens should be positioned on the image sensor surface.
In such a structure, however, the object surface on which an object is positioned, an lens system, and the image sensor should be aligned vertically with the direction of an optical axis. Therefore, the height of the optical sensor module inevitably increases, because of a limit in focal distance of the lens. Therefore, it is difficult to apply the optical sensor module to small-sized electronic apparatuses such as mobile phones which are gradually reduced in size.
To solve such a problem, Korea Patent Laid-open Publication No. 2006-34735 discloses a conventional optical sensor module (titled by ‘Ultra-slim Optical Joystick using Micro Array Lens Structure’).
FIG. 1 is a cross-sectional view of a conventional optical sensor module. The conventional optical sensor module includes a cover glass 11, a light source (LED) 12, an optical waveguide (illumination system) 13, a plano-convex lens 14, an image sensor 17, a printed circuit board (PCB) 18, and a barrel 19.
In the conventional optical sensor module, when a finger (object) 19 is placed on the surface of the cover glass 11, light irradiated onto the cover glass 11 is reflected by the object so as to be primarily concentrated by the plano-convex lens 14. Then, the light is secondarily concentrated by a micro lens array 15 such that an image is formed in a pixel of an imaging region 16.
In the conventional optical sensor module, a barrel (not shown) for fixing the lens 14 and a housing for fixing the barrel are separately used. Further, a retainer for adjusting a quantity of light incident from upward is needed in an upper portion of the lens 14 within the housing. Therefore, there is a limit in reducing the height of the module. Further, it is difficult to apply the optical sensor module to small-sized electronic apparatuses such as mobile phones which are gradually reduced in size.